Ti alloy for positive electrode for electrocoagulation printing, positive electrode and printing apparatus

ABSTRACT

A Ti alloy for a positive electrode for electrocoagulation printing contains, as a weight percentage, 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N, 0.3% or less of O, and Ti. The Ti alloy may further contain one or more elements selected from the group consisting of 0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, 1.0 to 6.0% of Mo, 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, 0.5 to 6.0% of V, 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight. A positive electrode for electrocoagulation printing has a surface composed of a Ti alloy containing Al.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a Ti alloy for use in a positive electrode for electrocoagulation printing, a positive electrode for electrocoagulation printing, an electrocoagulation printing apparatus, and a method for producing a printed matter.

[0003] 2. Description of the Related Art

[0004] Electrocoagulation printing is carried out as follows: (1) filling an electrocoagulation printing ink (referred to as an “ink” hereinafter) comprising an electrolytically coagulable polymer, a dispersing medium, a soluble electrolyte and a coloring agent from an ink feeding device between a positive electrode for electrocoagulation printing (referred to as a “positive electrode” hereinafter) having a surface made of, for example, a stainless steel and a printing head comprising a plurality of negative electrodes composed of many independent pin elements, (2) applying an electrical signal between the negative electrodes and positive electrode to coagulate the ink filled therebetween to form a plurality of coagulated ink dots representative of a desired image on the surface of the positive electrode, (3) removing the non-coagulated ink by means of a removal device for removing the non-coagulated ink from the surface of the positive electrode, and (4) allowing a web of a substrate to contact with the surface of the positive electrode, thus transferring coagulated ink dots from the surface of the positive electrode onto the surface of the web of the substrate (see re-publication of Patent Application WO 97/47474 and Japanese Unexamined Patent Application Publication No. 11-105270).

[0005] The mechanism for forming the coagulated ink dots on the surface of the positive electrode is as follows. Since stainless steel or aluminum that forms a passivated film is used for the positive electrode, trivalent ferric ions or aluminum ions as components of the positive electrode are dissolved by applying a voltage between the positive electrode and negative electrode as a result of the breakage of the passivated film at the portions where the voltage is applied. Since the ink used is coagulated by the trivalent ferric ions or aluminum ions, these trivalent ions dissolved from the positive electrode and mixed with the printing ink coagulate the ink.

[0006] The positive electrode has been manufactured in practice using stainless steel such as SUS 316 (comprising, by weight, 0.08% or less of C, 1.00% or less of Si, 2.00% or less of Mn, 0.045% or less of P, 0.030% or less of S, 10.00 to 14.00% of Ni, 16.00 to 18.00% of Cr, and 2.00 to 3.00% of Mo, with a balance of Fe) or SUS 304 (comprising, by weight, 0.08% or less of C, 1.00% or less of Si, 2.00% or less of Mn, 0.045% or less of P, 0.030% or less of S, 8.00 to 10.50% of Ni, and 18.00 to 20.00% of Cr, with a balance of Fe) since they have appropriate corrosion resistance and hardness.

[0007] Ghosts, or a phenomenon by which patterns that have been previously printed in high density appear on low density patterns when the low density patters are printed, are liable to occur by using the conventional stainless steel positive electrode, in addition to it being a great burden for maintenance such as repairing, due to its heavy weight.

SUMMARY OF THE INVENTION

[0008] The inventors of the present invention have devised, through studies of metallic materials suitable for the positive electrode that can reduce the occurrence of ghosts and that are lighter than stainless steel, a Ti alloy containing Al, being lightweight, being able to form a passivated film on its surface, and being excellent in corrosion resistance. It was found that this material is suitable for the positive electrode, and incidence of ghosts is less in a Ti alloy having a specified composition than in SUS 316 and SUS 304 that have been in practical use. The inventors also found that, in comparison with stainless steel, the material has similar degree of corrosion resistance as well as similar degree of ink film forming and peeling ability, ink removing ability and processibility, thereby completing the present invention.

[0009] In a first aspect, the present invention provides a Ti alloy for a positive electrode containing, as a weight percentage (wt. %), 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N, 0.3% or less of O, and Ti.

[0010] In a second aspect, the present invention provides a positive electrode having a surface composed of a Ti alloy containing Al.

[0011] In a third aspect, the present invention provides an electrocoagulation printing apparatus comprising a revolving positive electrode having a surface composed of a Ti alloy containing Al, an ink feeding device for feeding an ink onto the surface of the positive electrode, a printing head comprising a plurality of negative electrodes for forming coagulated ink dots representative of a desired image on the surface of the positive electrode by coagulating the ink by electrical energization, a removal device for removing non-coagulated ink from the surface of the positive electrode, and a transfer device for printing the image by transferring the coagulated ink dots from the surface of the positive electrode onto a substrate.

[0012] In a forth aspect, the present invention provides a method for producing a printed matter comprising the steps of:

[0013] a) providing a positive electrode having a surface composed of a Ti alloy containing Al and a plurality of negative electrodes;

[0014] b) providing an electrocoagulation printing ink between the positive electrode and the negative electrodes;

[0015] c) electrifying the positive electrode and selected ones of the negative electrodes to cause a coagulation of the ink on the surface of the positive electrode;

[0016] d) removing non-coagulated ink from the surface of the positive electrode to form an image on the surface of the positive electrode; and

[0017] e) transferring the image from the surface of the positive electrode onto a substrate to produce a printed matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a side view showing an example of the electrocoagulation printing apparatus according to the present invention.

[0019]FIG. 2 is a front view showing an example of the positive electrode according to the present invention.

[0020]FIG. 3 is a side view of the positive electrode shown in FIG. 2.

[0021]FIG. 4 is a cross section of the positive electrode shown in FIG. 2 along the line IV-IV.

[0022]FIG. 5 is a perspective view of the positive electrode shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The Ti alloy, positive electrode and electrocoagulation printing apparatus according to the present invention will be described in detail with reference to drawings. “Percent (%)” hereinafter refers to “Percent by weight (wt. %)”

[0024] The Ti alloy according to the present invention contains 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N, 0.3% or less of O, and Ti. The Ti alloy may optionally further contain one or more elements selected from the group consisting of 0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, 1.0 to 6.0% of Mo, 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, 0.5 to 6.0% of V, 0.1 to 1.0% of Si, and 0.005 to 0.10% of B. Preferably, one or more elements selected from a group I consisting of 0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, and 1.0 to 6.0% of Mo; and/or one or more elements selected from a group II consisting of 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, and 0.5 to 6.0% of V; and/or one or more elements selected from a group III consisting of 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, are optionally contained.

[0025] Preferable embodiments are exemplified below:

[0026] (1) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.3% or less of O, with a balance of Ti and inevitable impurities;

[0027] (2) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.3% or less of O, optionally containing one or more elements selected from the group I, optionally containing one or more elements selected from the group II, and optionally containing one or more elements selected from the group III, with a balance of Ti and inevitable impurities;

[0028] (3) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group I, with a balance of Ti and inevitable impurities;

[0029] (4) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group II, with a balance of Ti and inevitable impurities;

[0030] (5) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group III, with a balance of Ti and inevitable impurities;

[0031] (6) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group I, and one or more elements selected from the group II, with a balance of Ti and inevitable impurities;

[0032] (7) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group II, and one or more elements selected from the group III, with a balance of Ti and inevitable impurities;

[0033] (8) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group I, and one or more elements selected from the group III, with a balance of Ti and inevitable impurities; and

[0034] (9) a Ti alloy containing 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N and 0.03% or less of O, further containing one or more elements selected from the group I, one or more elements selected from the group II, and one or more elements selected from the group III, with a balance of Ti and inevitable impurities.

[0035] The Ti alloy according to the present invention having each composition as described above generates few ghosts when used as the material for the positive electrode besides being a considerably lighter metallic material for the positive electrode as compared with stainless steel. Moreover, the material is endowed with the same or a greater degree of corrosion resistance, ink film forming ability and peeling ability, ink removal performance and processibility as conventional articles.

[0036] The reason for the composition of the Ti alloy being selected as described above will be explained below.

[0037] [28.0 to 35.0% of Al]

[0038] Al is an element that is incorporated for supplying

[0039] Al³⁺ ions required for electrocoagulation printing. When the content of Al is less than 28.0%, or exceeds 35.0%, good ductility cannot be obtained, although a sufficient amount of Al³⁺ ions are supplied. Preferable content of al is 30.0 to 34.0%.

[0040] [0.1% or Less of C, 0.05% or Less of N, and 0.3% or Less of O]

[0041] It is preferable that the content of C, N and O is low since they are impurities. Ductility, corrosion resistance, formation of a passivated film, and release of Al³⁺ ions are less hindered when the content of C, N and O is 0.1% or less, 0.05% or less and 0.3% or less, respectively.

[0042] [0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, and 1.0 to 6.0% of Mo: Group I]

[0043] It is preferable to include at least one of the elements of Nb, Ta, Hf, Zr, W and Mo since they improve corrosion resistance. Since Nb and Ta do not form a third phase such as a β phase that deteriorates ductility at room temperature, they may be contained in high concentrations, enabling corrosion resistance to be further improved.

[0044] From the view point of improving corrosion resistance, the content of Nb and Ta is 0.5% or more, preferably 1.0% or more, the content of Hf and Zr is 0.1% or more, preferably 0.3% or more, and the content of W and Mo is 1.0% or more, preferably 3.0% or more. In order to prevent ductility from being reduced, the content of Nb and Ta is 15.0% or less, the content of Hf and Zr is 1.0% or less, and the content of W and Mo is 6.0% or less. The total content of Nb and Ta is preferably 0.5 to 15.0%, more preferably 1.0 to 10.0%, the total content of Hf and Zr is preferably 0.1 to 1.0%, more preferably 0.3 to 0.8%, and the total content of W and Mo is preferably 3.0 to 6.0%, more preferably 3.0 to 5.0%.

[0045] [0.5 to 6.0% of Cr, Mn and V: Group II]

[0046] It is preferable to include at least one of the elements of Cr, Mn and V, since they improve ductility. Their content should be 0.5% or more, or preferably 1.0% or more, from the viewpoint of allowing them to take effect. When the content exceeds 6.0%, on the other hand, a third phase such as a β-phase that decreases ductility at room temperature may be formed, and thereby ductility may be inhibited. Their preferable total content is 0.5 to 6.0%, more preferably 1.0 to 5.0%.

[0047] [0.1 to 1.0% of Si, and 0.005 to 0.10% of B: Group III]

[0048] Since Si forms silisides and B forms borides, both of which can improve abrasion resistance, it is preferable to include at least one of these elements. The content of Si and B is 0.1% or more and 0.005% or more, respectively, to allow them to take effect. Ductility may be inhibited when the content of Si and B exceeds 1.0% and 0.1%, respectively. The preferable content of Si is in the range of 0.3 to 0.8%, and that of B is 0.010 to 0.050%.

[0049] [Fe, Co, Ni, Cu, Y, and Rare Earth Elements (REM)]

[0050] It is preferable that the content of Fe, Co and Ni as impurities is low. Although small quantities of Cu, Y and REM have little effect on the properties of the alloy, too much content thereof decreases the toughness of the alloy and inhibits the manufacturing performance of a cylinder of the positive electrode. Therefore, low content of them is preferable.

[0051] One example of a method for manufacturing the Ti alloy will be described hereinafter. The Ti alloy may be formed into an ingot by melting it in a conventionally used furnace such as a plasma furnace (PPC furnace) and vacuum arc furnace, followed by casting thereafter. The Ti alloy to be used for the positive electrode is manufactured by applying a HIP treatment (hydrostatic press at a constant temperature), hot processing and cutting processing.

[0052] The positive electrode 2 shown in FIGS. 2 to 5 as one example of the present invention has a surface 4 composed of the Ti alloy containing Al, preferably one of the Ti alloys of the embodiments (1) to (9) as described above, and is rotated by a driving mechanism (not shown). A cylinder 3 is secured to a rotation cylinder shaft 5 with bolts 7 using a flange 6. At least the surface 4 of the cylinder 3 is composed of the Ti alloy containing Al. The entire cylinder 3 or the entire positive electrode 2 may also be composed of the Ti alloy containing Al. The surface 4 of the cylinder 3 is smooth, and is activated by breaking a passivated film by supplying an electric current between the positive electrode 2 and negative electrodes 12 (in FIG. 1), enabling coagulated ink dots to be formed.

[0053] The electrocoagulation printing apparatus 1, as shown in FIGS. 1 to 5 as one example of the present invention, comprises an ink feeding device 8 for feeding an ink onto the surface 4 of the positive electrode 2, a printing head 11 having a plurality of negative electrodes 12 composed of pin elements for forming coagulated ink dots representative of a desired image on the surface 4 of the positive electrode 2 by coagulating the ink by supplying an electric current, a removal device 13 for removing the non-coagulated ink from the surface 4 of the positive electrode 2, a transfer device 14 for printing the image by transferring the coagulated ink dots from the surface 4 of the positive electrode 2 onto a substrate (web W), a coating device 16 for coating the surface of the positive electrode 2 with an oily substance, if necessary, and a cleaning device 20 for cleaning the positive electrode 2.

[0054] The revolving positive electrode 2 has the structure mentioned above.

[0055] The ink feeding device 8 comprises a passageway (not shown) elongating in a longitudinal direction, a pipe 9 for feeding the ink into the passageway, and a plurality of nozzles 10 communicating with the passageway elongating in a longitudinal direction and feeding the ink. The ink containing an electrolytically coagulable polymer, a dispersion medium, a soluble electrolyte and a coloring agent is fed, from the nozzles 10, into a gap G between the surface 4 of the positive electrode 2 and the negative electrodes 12.

[0056] A plurality of negative electrodes 12 electrically insulated from one another are arranged in rectilinear alignment on the printing head 11. The negative electrodes 12 are spaced by the gap G from the positive electrode 2 so that they are disposed on a plane parallel to the longitudinal axis of the positive electrode 2. The ink is filled in the gap G between the electrodes 2 and 12 with the ink feeding device 8. An electric current is supplied to selected negative electrodes of the plural electrodes 12 on the printing head 11, and the ink is selectively coagulated and adheres to each point on the surface 4 of the positive electrode 2 facing the selected and electrically energized negative electrodes 12, while the positive electrode 2 is rotated.

[0057] The non-coagulated ink removal device 13 comprises a slender blade member made of an elastic material and a conduit type recovery mechanism (both not shown), and scrapes the non-coagulated ink off from the surface 4 of the positive electrode 2 by making the blade member press-contact with and slide on the surface of the positive electrode 2. The non-coagulated ink is removed from the side face of the cylinder using the conduit type recovery mechanism and recirculated back to the ink feeding device 8.

[0058] The transfer device 14 comprises a pressure roller 15 and a device (not shown) for allowing the pressure roller 15 to move in a direction toward the positive electrode 2 or in a direction away from the positive electrode 2. The pressure roller 15 causes a web W of the substrate to press-contact with the surface 4 of the positive electrode 2 on which the coagulated ink dots are formed, and is driven by the positive electrode 2 with the rotation thereof. Printing is performed by moving the web W in the direction of the arrow in FIG. 1.

[0059] A positive electrode coating device 16 for coating the surface of the positive electrode with an oily substance in advance of feeding the ink may be provided, if necessary, upstream of the ink feeding device 8. The positive electrode coating device 16 comprises a transfer roller 17 that is driven by the positive electrode 2 with its rotation and transfers an oily substance such as an olefinic substance on the surface 4 of the positive electrode 2, a feeding device 18 for feeding the oily substance onto the transfer roller 17, and a rotating brush 19 for smoothing the surface of the positive electrode 2 coated with the oily substance. The oily substance is transferred onto the surface 4 of the positive electrode 2 from the transfer roller 17, and the oily substance on the surface of the positive electrode 2 is spread evenly with the rotating brush 19.

[0060] A positive electrode cleaning device 20 provided when necessary removes all the coagulated ink dots remaining on the surface 4 of the positive electrode 2 after transferring the coagulated ink dots from the surface 4 of the positive electrode 2 onto the web W, and comprises a rotating brush 21 for scrubbing the surface 4 of the positive electrode 2, high pressure cleaning liquid jet nozzles 22 disposed at both sides of the rotating brush 21, and a cleaning liquid removal roller 23 for removing the cleaning liquid by rotating in the opposite direction to the positive electrode 2.

[0061] In FIG. 1, the reference numerals 24 denote legs, the reference numeral 25 denotes a base plate, the reference numerals 26 denote frames, the reference numeral 27 denotes a vertical plate, and reference numerals 28 denote guide rollers.

[0062] A printed matter by electrocoagulation printing can be produced according to the following method that comprises the steps of:

[0063] a) providing a positive electrode having a surface composed of a Ti alloy containing Al and a plurality of negative electrodes;

[0064] b) providing an electrocoagulation printing ink between the positive electrode and the negative electrodes;

[0065] c) electrifying the positive electrode and selected ones of the negative electrodes to cause a coagulation of the ink on the surface of the positive electrode;

[0066] d) removing any non-coagulated ink from the surface of the positive electrode to form an image on the surface of the positive electrode; and

[0067] e) transferring the image from the surface of the positive electrode onto a substrate to produce a printed matter.

[0068] Preferably, the method further comprises the steps of: after step a), coating the surface of the positive electrode with an oily substance; and after step e), cleaning the positive electrode to remove therefrom any remaining coagulated ink.

[0069] The printing apparatus comprising the positive electrode of the Ti alloy mentioned above can be utilized for applying this method.

[0070] Examples of the present invention will be described hereinafter.

EXAMPLE 1

[0071] The Ti alloys with the compositions in the examples and comparative examples listed in Table 1 below were manufactured into ingots with a diameter of 350 mm by re-melting and casting in a vacuum arc furnace after melting in a plasma furnace (PPC furnace) and casting. These ingots were subjected to HIP treatment for 20 hours in an Ar atmosphere at 1250° C. under a pressure of 1200 atm, and were hot-rolled at 1000° C. to a thickness of 300 mm. Plate specimens with a width of 50 mm and a thickness of 10 mm were cut from the cast sheet.

[0072] Test pieces (50 mm×50 mm×10 mm) for a non-coagulated ink removal test, coagulated ink film forming test and coagulated ink film peeling test, test pieces (20 mm×20 mm×10 mm) for a corrosion resistance test against acid and KCl solutions, and test pieces for a processibility test (50 mm×50 mm×10 mm) were sampled from the plate specimens, and were subjected to the tests by the following methods. The results are shown in Tables 2.

[0073] 1. Removal of Non-Coagulated Ink, Formation of Coagulated Ink Film, and Peeling of Coagulated Ink Film:

[0074] The entire surface of a SUS 316 plate that serves as a negative electrode was masked with an insulation tape with a thickness of 50 μm, and a window with an area of 1 cm×1 cm was open. An ink prepared from the following ingredients was filled into the window, and the SUS plate was laid on a test piece with dimensions of 50 mm×50 mm×10 mm so that the ink was sandwiched between the SUS plate and the test piece in order to subject it to a current flow test. A large magnitude of current was supplied using a capacitor since the area of the negative electrode is very different from that in practical printing, and the discharge time was adjusted to be of the same order as that used in practical printing. [Composition of the ink] Demineralized water  72.18 wt. % Carbon black sold under the trademark  10.49 wt. % Carbon Black Monarchs ® 120 Anionic dispersing agent sold under  1.78 wt. % the trademark CLOSPERSE 2500 Surfactant-free anionic acrylamide copolymer  6.99 wt. % sold under the trademark ACCOSTRENGTH 86, having a weight average molecular weight of about 250,000 and modified to exhibit a carboxyl content of about 12 wt. % Potassium chloride  8.39 wt. % Disodium EDTA dehydrate sold under  0.03 wt. % the trademark SEQUESTRENE NA2 Biocidal agent sold under the trademark  0.14 wt. % PARMETOL K-50 100.00 wt. %

[0075] Removal of Non-Coagulated Ink

[0076] The non-coagulated ink on the positive electrode after the current supply was scraped off with a blade, and the surface after scraping was observed by the naked eye. The surface of the positive electrode was evaluated by classifying it into 10 grades, comparing with the result of the same test for the SUS 316 plate, which was evaluated as grade 5 to form a standard.

[0077] Formation of Coagulated Ink Film

[0078] The surface of the positive electrode after scraping off the non-coagulation ink with the blade (the coagulated ink film) was observed by the naked eye, and evaluated by classifying it into 10 grades, comparing with the result of the same test for the SUS 316 plate, which was evaluated as grade 5 to form a standard.

[0079] Peeling of the Coagulated Ink Film

[0080] The coagulated ink film was peeled off with an adhesive tape, and the surface of the positive electrode was evaluated by classifying it into 10 grades, comparing with the result of the same test for the SUS 316 plate, which was evaluated as grade 5 to form a standard.

[0081] 2. Corrosion Resistance Test Against Acids and KCl Solutions

[0082] Each test piece with dimensions of 20 mm×20 mm×10 mm was stood upright, and four faces of the test piece except the top and bottom faces were finished by wet-grinding with a #1000 abrasive paper. Each test piece was embedded in an epoxy resin and, after curing the resin, it was cut at the center in a direction parallel to the two unpolished faces. The test face was finally finished by wet-grinding with the #1000 abrasive paper. These test pieces were immersed in 20 milliliters of each of the test solutions in a closed system. After one week, the surface of each test piece was observed by the naked eye, and evaluated by classification into 10 grades, comparing with the result of the same test for the SUS 316 plate, which was evaluated as grade 5 to form a standard.

[0083] 3. Processibility Test

[0084] A test piece with dimensions of 7 mm×7 mm×5 mm was cut from the processibility test piece with dimensions of 50 mm×50 mm×10 mm using a grindstone cutter, and the incidence of breakage at the edges was judged by the naked eye to evaluate processibility as good (G) or poor (NG). TABLE 1 (wt. &) No Al C N O OTHERS Ti EX-  1 29.0 0.05 0.03 0.13 — BALANCE AMPLE  2 33.7 0.04 0.03 0.13 — BALANCE  3 33.2 0.04 0.03 0.14 Nb: 4.8 BALANCE  4 32.8 0.03 0.02 0.16 Nb: 8.8 BALANCE  5 33.0 0.04 0.04 0.20 Nb: 13.3 BALANCE  6 33.6 0.05 0.02 0.14 Mo: 4.0 BALANCE  7 32.9 0.07 0.03 0.26 Nb: 0.5, BALANCE Ta: 2.0, W: 1.5  8 33.2 0.04 0.03 0.18 Cr: 2.2 BALANCE  9 33.4 0.06 0.03 0.16 Mn: 1.2, BALANCE V: 1.3 10 33.5 0.08 0.04 0.15 Cr: 4.2, BALANCE Mn: 0.8, V: 0.8 11 29.3 0.04 0.03 0.16 Si: 0.5 BALANCE 12 29.5 0.06 0.03 0.18 Si: 0.6, BALANCE B: 0.015 13 29.4 0.07 0.03 0.19 Nb: 0.7, BALANCE Cr: 3.2 14 29.2 0.07 0.03 0.20 Nb: 0.8, BALANCE Mo: 3.1, V: 2.5 15 29.6 0.06 0.04 0.22 Nb: 4.3, BALANCE W: 1.2, Mn 1.1 16 29.7 0.08 0.04 0.23 Nb: 7.8, BALANCE Si: 0.8 17 34.2 0.07 0.05 0.25 Mo: 3.8, BALANCE B: 0.019 18 34.3 0.04 0.02 0.18 Cr: 2.3, BALANCE Si: 0.7 19 34.2 0.05 0.03 0.15 V: 4.3, BALANCE B: 0.011 20 34.0 0.05 0.02 0.20 Nb: 2.2, BALANCE V: 2.1, Si: 0.8 21 34.9 0.06 0.02 0.13 Ta 8.0, BALANCE Mn: 2.2, B: 0.012 22 34.2 0.06 0.03 0.14 Nb: 12.0, BALANCE Ta: 3.1, Cr: 1.8 COMP.  1 36.4 0.04 0.03 0.13 — BALANCE EX-  2 26.5 0.05 0.03 0.20 — BALANCE AMPLE  3 28.5 0.06 0.03 0.18 Nb: 16.3 BALANCE  4 32.3 0.07 0.03 0.32 Mo: 7.5 BALANCE  5 31.4 0.13 0.03 0.22 Zr: 1.8 BALANCE  6 32.6 0.03 0.10 0.20 Cr: 7.4 BALANCE  7* — 0.06 0.01 0.18 Ni: 10.12, BALANCE Cr: 16.32, : Fe Mn: 0.82, Si: 0.32

[0085] TABLE 2 ACID CORROSION 13% KCl RESISTANCE CORROSION COAGULATED REMOVAL (7 DAYS) RESISTANCE INK FILM OF NON- H₂SO₄ HCl (7 DAYS) PROCESSI- FORMA- PEEL- COAGULA- INCIDENCE pH pH pH pH pH pH pH BILITY BY SPECIFIC No. TION ING TED INK OF GHOST 2 3 4 2 4 5.6 4.0 GRINDSTONE GRAVITY EXAMPLE 1 4 5 5 NONE 5 5 5 5 5 5 5 G 3.82 2 5 5 5 NONE 4 5 5 4 5 5 4 G 3.80 3 5 5 7 NONE 5 6 6 6 6 6 6 G 3.94 4 4 6 5 NONE 5 7 7 7 7 7 7 G 3.98 5 4 6 5 NONE 6 8 8 8 8 8 8 G 4.02 6 5 6 5 NONE 5 6 6 6 6 6 6 G 3.96 7 4 6 5 NONE 5 6 6 6 6 6 6 G 3.96 8 5 5 5 NONE 4 5 6 4 5 5 5 G 3.80 9 6 5 5 NONE 4 4 5 4 5 4 5 G 3.82 10 5 5 5 NONE 4 4 5 4 5 5 4 G 3.84 11 4 5 5 NONE 5 5 5 5 5 5 5 G 3.82 12 4 5 5 NONE 5 5 5 5 5 5 5 G 3.82 13 3 6 5 NONE 5 6 6 4 5 6 5 G 3.83 14 3 6 5 NONE 5 6 6 5 6 6 5 G 3.98 15 3 6 5 NONE 5 6 6 5 6 6 5 C 3.87 16 3 6 5 NONE 5 7 7 7 7 7 6 G 3.98 17 5 6 5 NONE 6 7 7 7 7 7 6 G 3.96 18 5 5 5 NONE 4 5 6 4 5 5 5 G 3.81 19 5 5 5 NONE 4 6 6 4 5 5 4 G 3.82 20 5 5 5 NONE 4 6 6 4 5 5 4 G 3.82 21 4 6 5 NONE 4 5 6 4 5 5 4 G 4.10 22 5 6 5 NONE 6 7 8 7 8 8 7 G 3.95 COMP. 1 5 5 5 NONE 3 3 4 3 4 4 3 NG 3.78 EXAMPLE 2 2 7 5 NONE 2 3 5 3 4 5 4 NG 3.86 3 2 8 5 NONE 6 6 7 6 7 7 7 NG 3.80 4 5 6 5 NONE 5 5 6 5 6 6 5 NG 3.93 5 5 5 5 NONE 5 5 5 5 5 5 5 NG 3.81 6 5 5 5 YES 4 5 5 5 5 5 4 NG 3.84 7 5 5 5 YES 5 5 5 5 5 5 5 G 7.9

[0086] As shown in Table 2, the coagulated ink film forming ability of each sample in all examples was evaluated to be of grades 3 to 6 in comparison with the grade 5 of the SUS 316 plate in Comparative Example 7. They pose no problem for printing since the sample with grade 3 or higher is possible for use in printing in combination with electrochemical auxiliary measures. Furthermore, it was possible in the examples to obtain a coagulated ink film with better film forming ability than the film on the SUS 316 plate in Comparative Example 7, by combining with the electrochemical auxiliary measures. In contrast, the samples in Comparative Examples 2 and 3, in which the Al content does not satisfy the prescribed content in the present invention, gave evaluations of grade 2, and were not suitable for use as the positive electrode.

[0087] Peeling of the coagulated ink and removal of non-coagulated ink were evaluated as grade 5 or more with no problems in practical use, both in the examples and comparative examples.

[0088] Ghosts were observed in the images obtained in Comparative Example 7 using the SUS 316 plate and in Comparative Example 6 using the sample with a Cr content greater than the prescribed level in the present invention, while no ghosts were observed in the samples in the examples and other comparative examples.

[0089] Since corrosion resistance against the acids and 13% KCl solutions were evaluated as grades 4 to 7 in the examples, it was possible to use the samples for the positive electrode. In contrast, the sample in Comparative Example 1 with a greater content of Al than the prescribed content of the present invention and the sample in Comparative Example 2 with a lower content of Al than the prescribed content in the present invention provided results of grade 3 or lower, showing that both samples could not be used for the positive electrode.

[0090] No problems were encountered in processibility using the grindstone cutter in the samples of the examples and Comparative Example 7 using the SUS 316 plate. In contrast, the samples in Comparative Examples 1 and 2, and the samples in Comparative Examples 3, 4, 5 and 6 with the content of Nb, Mo, Zr and Cr greater than the prescribed content in the present invention were fragile and had some problems in cutting processibility.

[0091] While the samples in the examples, and the samples in the comparative examples except the sample in Comparative Example 7 had specific gravities in the range of 3.80 to 4.10, the sample in Comparative Example 7 showed a specific gravity of 7.9.

EXAMPLE 2

[0092] The Ti alloy with a composition No. 3 in the examples shown in Table 1 was melted in a plasma furnace (PPC furnace) and, after casting, re-melted in a vacuum arc furnace to obtain an ingot with a diameter of 350 mm and an weight of 500 kg by casting. The ingot was subjected to a HIP treatment for 20 hours at 1250° C. in an Ar atmosphere at 1200 atm, and a columnar Ti alloy material with a diameter of 320 mm was manufactured by hot-forging at 1000° C.

[0093] The Ti alloy material was machined into a cylinder with an outer diameter of 300 mm, an inner diameter of 260 nm, and a length of 550 mm.

[0094] The cylinder 3 was assembled into a positive electrode as shown in FIGS. 2 to 5, and the positive electrode obtained was attached to the electrocoagulation printing apparatus for electrocoagulation printing as shown in FIG. 1 to be used in conducting printing.

[0095] As a result, no ghosts were observed on the printed matter. The quality of the printed matter was remarkably excellent as compared with printing using the conventional cylinder made of SUS 316. The weight of the positive electrode cylinder was 36.8 kg which is 48% of the conventional cylinder made of SUS 316.

[0096] The present disclosure relates to subject matter contained in Japanese Patent Application P2000-093993, filed on Mar. 30, 2000, the disclosure of which is expressly incorporated herein by reference in its entirety.

[0097] It is to be noted that, besides those already mentioned above, many modifications and variations of the above embodiments may be made without departing from the novel and advantageous features of the present invention. Accordingly, all such modifications and variations are intended to be included within the scope of the appended claims. 

What is claimed is:
 1. A Ti alloy for a positive electrode for electrocoagulation printing containing, as a weight percentage, 28.0 to 35.0% of Al, 0.1% or less of C, 0.05% or less of N, 0.3% or less of O, and Ti.
 2. A Ti alloy according to claim 1, further containing at least one element selected from the group I consisting of 0.5 to 15.0% of Nb, 0.5 to 15.0% of Ta, 0.1 to 1.0% of Hf, 0.1 to 1.0% of Zr, 1.0 to 6.0% of W, and 1.0 to 6.0% of Mo, by weight.
 3. A Ti alloy according to claim 1, further containing at least one element selected from the group II consisting of 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, and 0.5 to 6.0% of V, by weight.
 4. A Ti alloy according to claim 2, further containing at least one element selected from the group II consisting of 0.5 to 6.0% of Cr, 0.5 to 6.0% of Mn, and 0.5 to 6.0% of V, by weight.
 5. A Ti alloy according to claim 1, further containing at least one element selected from the group III consisting of 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight.
 6. A Ti alloy according to claim 2, further containing at least one element selected from the group III consisting of 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight.
 7. A Ti alloy according to claim 3, further containing at least one element selected from the group III consisting of 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight.
 8. A Ti alloy according to claim 4, further containing at least one element selected from the group III consisting of 0.1 to 1.0% of Si, and 0.005 to 0.10% of B, by weight.
 9. A positive electrode for electrocoagulation printing having a surface composed of a Ti alloy containing Al.
 10. A positive electrode according to claim 9, wherein the Ti alloy containing Al is the Ti alloy of claim
 1. 11. An electrocoagulation printing apparatus comprising a revolving positive electrode having a surface composed of a Ti alloy containing Al, an ink feeding device for feeding an ink onto the surface of the positive electrode, a printing head comprising a plurality of negative electrodes for forming coagulated ink dots representative of a desired image on the surface of the positive electrode by coagulating the ink by electrical energization, a removal device for removing non-coagulated ink from the surface of the positive electrode, and a transfer device for printing the image by transferring the coagulated ink dots from the surface of the positive electrode onto a substrate.
 12. An electrocoagulation printing apparatus according to claim 11, wherein the Ti alloy containing Al is the Ti alloy of claim
 1. 13. A method for producing a printed matter comprising the steps of: a) providing a positive electrode having a surface composed of a Ti alloy containing Al and a plurality of negative electrodes; b) providing an electrocoagulation printing ink between the positive electrode and the negative electrodes; c) electrifying the positive electrode and selected ones of the negative electrodes to cause a coagulation of the ink on the surface of the positive electrode; d) removing non-coagulated ink from the surface of the positive electrode to form an image on the surface of the positive electrode; and e) transferring the image from the surface of the positive electrode onto a substrate to produce a printed matter.
 14. A method according to claim 13, wherein the Ti alloy containing Al is the Ti alloy of claim
 1. 